openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 78 insertions, 0 deletions

diff --git a/arch/powerpc/boot/mpc8xx.c b/arch/powerpc/boot/mpc8xx.c
new file mode 100644
index 000000000..e19ef64df
--- /dev/null
+++ b/arch/powerpc/boot/mpc8xx.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MPC8xx support functions
+ *
+ * Author: Scott Wood <scottwood@freescale.com>
+ *
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ */
+
+#include "ops.h"
+#include "types.h"
+#include "fsl-soc.h"
+#include "mpc8xx.h"
+#include "stdio.h"
+#include "io.h"
+
+#define MPC8XX_PLPRCR (0x284/4) /* PLL and Reset Control Register */
+
+/* Return system clock from crystal frequency */
+u32 mpc885_get_clock(u32 crystal)
+{
+	u32 *immr;
+	u32 plprcr;
+	int mfi, mfn, mfd, pdf;
+	u32 ret;
+
+	immr = fsl_get_immr();
+	if (!immr) {
+		printf("mpc885_get_clock: Couldn't get IMMR base.\r\n");
+		return 0;
+	}
+
+	plprcr = in_be32(&immr[MPC8XX_PLPRCR]);
+
+	mfi = (plprcr >> 16) & 15;
+	if (mfi < 5) {
+		printf("Warning: PLPRCR[MFI] value of %d out-of-bounds\r\n",
+		       mfi);
+		mfi = 5;
+	}
+
+	pdf = (plprcr >> 1) & 0xf;
+	mfd = (plprcr >> 22) & 0x1f;
+	mfn = (plprcr >> 27) & 0x1f;
+
+	ret = crystal * mfi;
+
+	if (mfn != 0)
+		ret += crystal * mfn / (mfd + 1);
+
+	return ret / (pdf + 1);
+}
+
+/* Set common device tree fields based on the given clock frequencies. */
+void mpc8xx_set_clocks(u32 sysclk)
+{
+	void *node;
+
+	dt_fixup_cpu_clocks(sysclk, sysclk / 16, sysclk);
+
+	node = finddevice("/soc/cpm");
+	if (node)
+		setprop(node, "clock-frequency", &sysclk, 4);
+
+	node = finddevice("/soc/cpm/brg");
+	if (node)
+		setprop(node, "clock-frequency", &sysclk, 4);
+}
+
+int mpc885_fixup_clocks(u32 crystal)
+{
+	u32 sysclk = mpc885_get_clock(crystal);
+	if (!sysclk)
+		return 0;
+
+	mpc8xx_set_clocks(sysclk);
+	return 1;
+}